172 Mr. Griffith, on the Order of Succession of the Older 
limestone, and underlying black carboniferous slate, inter- 
stratified with thin beds of limestone, which is ultimately 
succeeded by limestone without admixture ; the whole of the 
strata dipping to the south. Again, on the south side of the 
river Roughty, immediately to the east of Roughty Bridge, 
a similar succession of strata is observed dipping to the north. 
In this locality, the yellow sandstone contains that variety of 
calamite which is characteristic of the rock, and which is also 
abundant at Brickeen Island, near Killarney, and in the same 
geological position, underlying the limestone of the several 
troughs of the counties of Waterford and Cork. In the car- 
boniferous slate of Roughty Bridge, Retepora membranacea 
was observed. I shall mention one other locality in which 
the strata in connexion with the yellow sandstone have been 
observed in the valley of the river Roughty, namely, at the 
pier at Kenmare. At low water in this place, gray quartz rock 
and black carboniferous slate may be observed dipping to the 
north under the lower beds of the carboniferous limestone, 
which are exposed to view in an adjoining quarry. Imme- 
diately to the south of this quartz rock and slate, no rocks 
are visible, the strata being concealed by sand; but in a very 
short distance, beds of yellowish green slate, alternating with 
red slate and red limestone, occur which are identical with 
the strata visible in the localities already mentioned under- 
lying the yellow sandstone : no doubt can therefore be enter- 
tained that this rock is continuous on the south side of the 
valley from Kenmare pier to Roughty Bridge. It is true, in 
this locality, as well as in most others, that the yellow sand- 
stone has not been seen at the surface throughout the entire 
length of the carboniferous limestone trough, as, owing to 
a thick covering of diluvial matter, or of bog, the precise 
boundary between the base of the limestone series and the 
old red sandstone rocks is rarely visible; but as the yel- 
low sandstone and dark gray carboniferous slate do occur 
in every place where the outer boundary of the limestone 
series is exposed to view, I feel little doubt that these rocks 
equally occur in those positions where they are concealed from 
our view. If geologists were only to mark the limits of their 
rock districts in the precise localities in which the contacts 
are visible, no geological map could be formed. In maps on 
a large scale, the observed contacts might be shown by con- 
tinuous, and the supposed by dotted lines : but on a general 
map, though desirable, it would be impossible to enter into 
such detail, or if attempted it would be impracticable, on a map 
on which the features of the country are shown, to distinguish 
between the continuous and the dotted lines. 
